When a conventional flat knitting machine knits a fabric, it usually employs a plurality of intarsia yarn feeders to form special intarsia on the fabric. In order to efficiently knit complicated intarsia combinations on the fabric, the flat knitting machine commonly uses computer to control movement and operation of the intarsia yarn feeders. To prevent a lower knitting needle to hook a yarn delivered through a yarn feeding aperture of the intarsia yarn feeder to generate erroneous knitting during movement of the intarsia yarn feeder or after the intarsia knitting operation is finished, design of the intarsia yarn feeder not only provides a state of supplying the yarn via the yarn feeding aperture to the knitting needle for intarsia knitting, but also includes another state of moving the yarn feeding aperture away from the aforesaid position so that the knitting needle does not hook the yarn from the yarn feeding aperture.
The conventional intarsia yarn feeder mainly adopts a swinging approach to move the yarn from the yarn feeding aperture away the knitting needle. For instance, U.S. Pat. No. 6,981,393 discloses yarn feeders of flat knitting machine that includes a yarn feeder case slidable on a yarn guide rail at the upper portion of a needle bed and a driven mechanism to selectively perform linkage movements. The yarn feeder case has a switching mechanism that can be swung to switch a yarn feeding aperture between a yarn feeding position and a waiting position. The switching mechanism also can be swung on the yarn feeder case and move a pivotal rod up and down to support the middle portion of a yarn feeding rod. The yarn feeding aperture is formed at the lower end of the yarn feeding rod while the middle portion forms a swing operating portion, and the upper end forms a pressing portion to overcome the lifting elastic force to lower the yarn feeding aperture to a yarn supply position. It further has a setting device to set lift return of the swinging operating portion. When the yarn feeding aperture is located at the yarn supply position and the yarn feeding rod is moved downwards, the swinging operating portion set by the setting device is switched to an upward direction for returning.
In addition to the aforesaid technique that adopts depressing a selected rod to swing to form skew swing of the yarn feeding rod, there are other techniques to move the yarn feeding rod, such as using a gear to drive movement of the yarn feeding rod. European patent No. EP 1788132 discloses a yarn feeder for a flat knitting machine that can be moved longitudinally along a yarn feeder guide track via a transmission pulley mounted on a triangular slide rack, and also has a yarn feeder arm movable reciprocatedly between a yarn feeding position and at least one yarn feeding stopping position. The yarn feeder has at least one adjustment element for the yarn feeder arm that has a gear acting on a second adjustment element via a pinion to adjust the movement of the yarn feeder arm.
The aforesaid conventional techniques adopt different designs to drive the yarn feeder arm. As operation of the conventional intarsia yarn feeder is complex, multiple types of adjustment elements have to be designed and assembled to swing the yarn feeder arm. Hence fabrication and assembly costs are higher. Moreover, due to adjustment elements are numerous, they are prone to generate interference among them in movements that could interrupt operation of the yarn feeder arm.